1. Field of the Invention
The present invention relates to a recording medium suitable for recording with aqueous ink, particularly to a recording medium suitable for ink-jet recording.
2. Related Background Art
Ink jet recording is a method for recording images and letters by ejecting fine droplets of ink onto a recording medium such as a paper a sheet. Ink jet recording is rapidly becoming popular in recent years for various applications because of its high recording speed, ease of multicolor recording, flexibility in pattern recording, and because image fixation is not needed. Multicolor ink-jet recording is coming to be used in full color image recording since it is capable of giving images comparable with images formed by multicolor gravure printing or color photography, and is less expensive than multicolor printing when the number of reproduction is small. With improvements in recording speed, fineness of recording, and full color recording, the recording medium is required to have better qualities in addition to the improvements of the recording apparatus and the recording method.
Hitherto, various types of recording mediums have been disclosed. For example, recording sheets having a layer containing alumina hydrate of pseudo boehmite structure are disclosed in U.S. Pat. Nos. 4,879,166 and 5,104,730, and Japanese Patent Laid-Open Application Nos. 2-276670, 4-37576, and 5-32037. The prior art recording mediums involve disadvantages as follows: occurrence of beading of ink dots, due to insufficient absorbency for a large amount of ink in color image printing; likelihood of being scratched by a sheet delivery device due to insufficient surface hardness; likelihood of the ink-receiving layer surface cracking due to insufficient bonding strength of the ink-receiving layer; low circularity of printed dots cracking due to insufficient uniformity of the ink-receiving layer; and low gloss of recording medium due to less orientation of the pigment.
The beading mentioned in the present invention refers to a phenomenon in which dots irregularly move in the plane direction of the surface of an ink-receiving layer when the ink is still fluid before it is fixed in the ink-receiving layer.
The present invention has been made to offset the above disadvantages.
An object of the present invention is to provide a recording medium which has high ink absorbency to absorb ink at a higher absorbing rate and having higher surface hardness to be less liable to cracking on the surface.
Another object of the present invention is to provide a recording medium which is capable of forming an image with high circularity of dots and high gloss of the recorded image.
A still another object of the present invention is to provide a recording medium which provides water fastness and light fastness of the recorded image with less migration of the ink, in addition to the aforementioned properties.
A further object of the present invention is to provide a process for producing the aforementioned recording medium.
A still further object of the present invention is to provide an ink-jet recording method employing the aforementioned recording medium.
According to an aspect of the present invention, there is provided a recording medium having a porous ink-receiving layer containing alumina hydrate of boehmite structure formed on a base material, the alumina hydrate having crystallinity ranging from 15 to 80.
According to another aspect of the present invention, there is provided a recording medium having a porous ink-receiving layer containing alumina hydrate of boehmite structure formed on a base material, wherein microcrystals of the alumina hydrate are directed to be parallel to the plane direction of the ink-receiving layer at a parallelization degree of not less than 1.5.
According to still another aspect of the present invention, there is provided a recording medium having a porous ink-receiving layer containing alumina hydrate of boehmite structure formed on a base material, the alumina hydrate having crystallinity ranging from 15 to 80, and the microcrystals of the alumina hydrate being directed to be parallel to the plane direction of the ink-receiving layer at a parallelization degree of not less than 1.5.
According to a further aspect of the present invention, there is provided an ink-jet recording method employing the above recording medium.
According to a still further aspect of the present invention, there is provided a process for producing a recording medium having a porous ink-receiving layer containing alumina hydrate of boehmite structure, comprising the steps of: applying a coating liquid containing alumina hydrate of boehmite structure with shearing stress onto a base material; and drying the coated material to obtain the degree of parallelization of the microcrystal of the alumina hydrate with the plane direction of the ink-receiving layer of not less than 1.5.
According to a still further aspect of the present invention, there is provided a process for producing a recording medium, comprising the steps of: applying a liquid dispersion containing alumina hydrate of boehmite structure having crystallinity ranging from 15 to 80 onto a base material; and drying the coated material at a relative humidity of 20 to 60% to obtain crystallinity of the alumina hydrate ranging from 15 to 80 in the recording medium.
According to a still further aspect of the present invention, there is provided a process for producing a recording medium, comprising the steps of: applying a liquid dispersion containing alumina hydrate of boehmite structure having crystallinity of lower than 15 onto a base material; and drying the coated material at a relative humidity of 10 to 20% to obtain crystallinity of the alumina hydrate ranging from 15 to 80 in the recording medium.
According to a still further aspect of the present invention, there is provided a process for producing a recording medium comprising the steps of: applying a liquid dispersion containing alumina hydrate of boehmite structure having crystallinity of lower than 15 on a base material; and heating the coated material at a relative humidity of 10 to 20% to obtain crystallinity of the alumina hydrate ranging from 15 to 80 in the recording medium.